Family Chat (2.0): a built-in messenger for the family, phase 1

- Chat tab: direct chats and groups, text, attachments, replies, reactions, edit and delete, unread counts, search, drafts, mute and archive
- Live delivery over server-sent events; phone push for people who are not in the app (muted chats stay quiet)
- chat.js keeps conversations and files in data/chat; push.notify sends one person a notification
- Roadmap updated: phase 1 done, combined inbox with Signal still to do

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/boot.js

@@ -18,7 +18,7 @@
   setInterval(checkForUpdate, 10 * 60e3);
   await loadMe();
   await loadSettings();
-  sgStart();
+  sgStart(); if (typeof chStart === 'function') chStart();
   addEventListener('hashchange', route);
   restorePlayer();
   route();